Asynchrony among plant communities stabilises ecosystem

18 December 2017

Fluctuations in individual plant communities contribute to the stability of an ecosystem as a whole, a study published in Ecology Letters shows. Nadia Soudzilovskaia and colleagues for the first time used data from plant communities across five continents to prove this hypothesis.

Stable ecosystems

The composition of a plant community is an important factor for the functioning of an ecosystem, with different species contributing differently to the ecosystem. To better understand ecosystems, it is important to know what makes a plant community function stably at the long term. From year to year, the number of species in a plant community will not change significantly, but biomasses of individual species fluctuate between years. Rapid transitions in plant community composition and structure happen very seldom, but still, some ecosystems are more stable than others.

Soudzilovskaia explains: ‘We have tested the hypothesis that an ecosystem as a total is more stable if individual plant communities that constitute the ecosystem are fluctuating asynchronically. For example, if in one plant community the biomass increases, the biomass of another will not change, or it will decrease. This results in a different pattern every year.’ In unstable ecosystems, all plant communities fluctuate simultaneously, responding to the same driver.

Collecting for decades

Soudzilovskaia and her colleagues have assembled very large datasets from different types of grasslands from all the continents, collected by many researchers from about 50 universities. Changes in biomass of local plant communities and of metacommunities were measured. Soudzilovskaia and her colleagues submitted some of the oldest data, collected from the Caucasus Mountains over the last thirty years.

Revolutionary research

The research team showed that the hypothesis was indeed correct. Fluctuations in individual communities that constitute large ecosystems contribute to the stability of the ecosystem as a whole.

The confirmation of their hypothesis is revolutionary for ecological sciences. Soudzilovskaia: ‘Many ecological questions have theoretical answers. It regularly happens that when these answers are tested on real data representative for different ecological conditions, the theoretical frameworks actually don’t work.’